The Alphavirus genus includes a variety of viruses all of which are members of the Togaviridae family. The alphaviruses include Eastern Equine Encephalitis virus (EEE), Venezuelan Equine Encephalitis virus (VEE), Everglades virus, Mucambo virus, Pixuna virus, Western Equine Encephalitis virus (WEE), Sindbis virus, Semliki Forest virus, Middelburg virus, Chikungunya virus, O'nyong-nyong virus, Ross River virus, Barmah Forest virus, Getah virus, Sagiyama virus, Bebaru virus, Mayaro virus, Una virus, Aura virus, Whataroa virus, Babanki virus, Kyzylagach virus, Highlands J virus, Fort Morgan virus, Ndumu virus, and Buggy Creek virus. The viral genome is a single-stranded, messenger-sense RNA, modified at the 5′-end with a methylated cap, and at the 3′-end with a variable-length poly (A) tract. Structural subunits containing a single viral protein, C, associate with the RNA genome in an icosahedral nucleocapsid. In the virion, the capsid is surrounded by a lipid envelope covered with a regular array of transmembranal protein spikes, each of which consists of a heterodimeric complex of two glycoproteins, E1 and E2. See Pedersen et al., J. Virol. 14:40 (1974). The Sindbis and Semliki Forest viruses are considered the prototypical alphaviruses, and have been studied extensively. See Schlesinger The Togaviridae and Flaviviridae, Plenum Publishing Corp., New York (1986). The VEE virus has been studied by the present inventors. See U.S. Pat. No. 5,185,440 to Davis et al.
The study of these viruses has led to the development of beneficial techniques for vaccinating against the alphavirus diseases, and other diseases through the use of alphavirus vectors for the introduction of foreign DNA. See U.S. Pat. No. 5,185,440 to Davis et al., and PCT Publication WO 92/10578. The introduction of foreign DNA into eukaryotic cells has become a topic of increasing interest. It is well known that live, attenuated viral vaccines are among the most successful means of controlling viral disease. However, for some virus pathogens, immunization with a live virus strain may be either impractical or unsafe. One alternative strategy is the insertion of sequences encoding immunizing antigens of such agents into a vaccine strain of another virus. One such system utilizing a live VEE vector is described in U.S. Pat. No. 5,505,947 to Johnston. et al. Another such system is described by Hahn et al., Proc. Nati. Acad. Sci. USA 89:2679 (1992), wherein Sindbis virus constructs express a truncated form of the influenza hemagglutinin protein. Unfortunately, relatively few such systems are currently available.
Accordingly there remains a need in the art for nucleic acid sequences encoding foreign antigens into a vaccine strain of a virus which may be utilized as a vaccine for the foreign antigen, and/or the viral vector itself.